Capped octahedron coordination structures

The structures are known for a number of these compounds thus, of the eight-coordinate compounds, Eu(acac)3(phen) is square antiprismatic, Eu(dpm)3(py)2 and Nd(tta)3(Ph3PO)2 are dodecahedral seven-coordinate Lu(dpm)3(3-picoline) is a face-capped trigonal prism and Eu(dpm)3(quinuclidine) a capped octahedron. Nine-coordination is found in Eu(dpm)3(terpy) and also in Pr(facam)3(DME)3(facam = 3-trifluoroacetyl-D-camphorate). 

Tlie Re complexes, generally prepared by X2 oxidative addition to the parent Re species (equation 6), are normally seven coordinate and diamagnetic with a capped octahedron structure, but six-coordinate, 16-electron derivatives have been found, especially with isocyanide ligands. see Structure Property Maps for Inorganic Solids). 

Amines, hydrazines, and hydroxylamines. Amine complexes are known for tetravalent complexes of the earliest actinides (Th, U), particularly for the halides, nitrates, and oxalates. The complexes are generated either in neat amine, or by addition of amine to the parent compound in a nonaqueous solvent. Some of the known simple amine compounds are presented in Table 6. The molecular structure of ThCl4(NMe3)3 has been determined. The coordination environment about the metal is a chloride capped octahedron. A very limited number of adducts exist in which a tetravalent actinide is coordinated by a hydrazine or hydroxylamine ligand the parent compound is generally a halide or sulfate complex. Cationic metal hydrates coordinated with primary, secondary, or tertiary amines have also been isolated with acetylacetonate, nitrate, or oxalate as counterions. 

The three low energy structures available to 7-coordinate compounds are the pentagonal bipyramid, the capped octahedron and the capped trigonal prism. These structures are illustrated in Fig. 24. 

Pentagonal Bipyramid Capped Octahedron Capped Trigonal Prism Fig. 24. Low energy structures of 7-coordinate complexes... 

The starting point for the consideration of seven coordination is three structures with very similar stabilities the pentagonal bipyramid, capped octahedron, and capped... 

Structures of an interesting pair of hexamethylphosphoramide complexes where the coordinated anion is nitrosodicyanomethanide [X, O—N=C(CN)2] have been obtained. Thus [NdX3 OP(NMe2)3 4] is a seven-coordinated distorted capped octahedron, where X is monodentate via oxygen, while [YbX2 OP(NMe2)3 4] is nearly irons octahedral with Yb—O (hmpa) = 2.197 A average. 

Reported rhenium complexes possess one [70-74], two [75], and three [75] dithiocarboxylato ligands coordinated to the one rhenium atom to form a high coordination state, as in the case of the technetium complex [76]. One of these complexes 29 is synthesized from Re(VII)S4 and (PhCSS)2 (Fig. 10) [72]. An internal redox reaction occurs and Re( VII) is reduced to Re(III) in the synthetic process. Addition of sulfur-abstracting reagents, Ph3P or Et4NCN, produces the heptacoordinate complex 30 with the neutral capped octahedron structure or... 

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